1. Field
Methods and apparatuses consistent with exemplary embodiments relate to an electronic device using a photoplethysmogram (PPG) sensor for health monitoring such as cardiac health monitoring, renal dysfunctions, etc., of a person, and a method of operating the electronic device, and more particularly, to a method and electronic device for cuff-less Blood Pressure (BP) measurement.
2. Description of Related Art
Hypertension is known to be one of the silent health disorders with a potentially fatal outcome. Symptoms of hypertension are often not detectable until late stages of the disease. Consequently, most individuals are not aware of the disease progression, leading to conditions such as cardiovascular disease, renal dysfunction, etc. Although regular BP checkups at clinics are expected after a certain age, this certain age may not be accurate for most individuals due to the fast paced nature of an urban lifestyle. Also, it has been found that 20% of the patients register at doctor's clinic are for higher BP concerned compared to home settings. Home monitoring of the BP offers an advantage in terms of providing a familiar environment to hypertension patients. Evidence suggests periodic and continuous monitoring of BP can help in early detection of hypertension, thereby reducing mortality. With growing usage of smartphones equipped with PPG sensors, cuff-less BP measurement using a smartphone is feasible.
BP provides a measure of peripheral resistance in blood vessel and is closely related to cardiac function. The upper limit is defined as systolic blood pressure (SBP) while lower limit is defined as diastolic blood pressure (DBP). Sphygmomanometers are the most commonly used devices to accurately measure BP. Although sphygmomanometers are still considered the gold standard for measuring BP, they are mostly confined to clinical set-ups with medical/paramedical staff operating these devices. The method requires the user (i.e., doctor/patient) to inflate the cuff beyond a certain mercury level and auscultate to record the point correctly. This method requires proper training and is not ideal for self-use and continuous monitoring of BP. Further, the devices equipped with cuffs are not portable, and also do not offer on demand measurement capability/continuous monitoring of the BP. This results in a decrease in the reliability of the results obtained by these cuffed devices.
There also exist several methods in which a smartphone based cuff-less BP estimation can operate to check the feasibility of cuff-less BP monitoring through PPG sensor data. The reports obtained based on the PPG sensor data are analyzed and classified into pure PPG signal based, or hybrid approaches comprising both PPG and ECG signals. In another method, smartphones using two PPG sensors located at a known distance are used to estimate pulse wave velocity (PWV) to derive the BP of the user.
In yet another method, the relationship between BP and elasticity of arterial blood vessels (Moens-Kortweg equation) is used to obtain a linear relationship between pulse wave transfer time (PWTT) and BP to correctly estimate the BP. In yet another method, it is possible to compute pulse transit time (PTT) by placing PPG and ECG sensors on finger tips to estimate the BP, and compute the PTT by placing the PPG sensor in an ear lobe and an ECG sensor on the chest The BP estimation using the PTT based approach is more cumbersome, as it requires data from two sensors positioned at different locations on the human body, and this method is also prone to errors because calibration of individual physiological parameters is required. Thus, the aforementioned method(s) is/are dependent on PWV or PTT estimation to estimate the BP.